This invention relates to a method for manufacturing anode cylinders of electron tubes, such as transmitting tubes, magnetrons, X-ray tubes, klystrons, etc.
As is generally known, the anode of a magnetron for a microwave oven, for example, is formed of an anode cylinder, a plurality of anode vanes radially arranged on the inner face of the cylinder, and resonance cavities as many as the vanes. Available as the material for the anode are copper, aluminum, etc. which have high electric and thermal conductivity characteristics. In general, copper is preferred because of its higher heat resistance. In one conventional method for manufacturing the magnetic anode, an anode cylinder of a given length is cut from an elongated cylinder material, the inner and outer faces and both open end faces of the anode cylinder are cut into predetermined configurations, and anode vanes are brazed to the inner peripheral face of the cylinder. In another conventional method, a copper material is forced into a given die, and an anode cylinder and vanes are integrally extruded in a cold hobbing process. In the former method, however, the manufacture of the cylinder material requires much labor and costs a great deal to make the product expensive. Further, manufacturers of magnetrons will not be allowed freely to change the inner or outer diameter of the anode cylinder. In the latter method, on the other hand, a lot of trimmed material is cast away to reduce the coefficient of material utilization, and the die for the cold hobbing process is very susceptible to abrasion, resulting in an increase in manufacturing cost.
Accordingly, there has already been proposed a method for the manufacture of the magnetron anode in which an anode cylinder is formed by rolling up a plate piece or material and vanes are bonded to the inner face of the anode cylinder. This method facilitates the procurement and manufacture of material, and can enjoy redesigning of the cylinder, that is, change of the cylinder diameter and/or thickness. With this method, moreover, the coefficient of material utilization is approximately 100%. One such method for manufacturing an anode including the rolling process is disclosed in Japanese Utility Model Disclosures (KOKAI) Nos. 48-90464, 49-11659, 49-67545, 50-157854, 50-157855 and 51-121160, and U.S. Pat. No. 4,163,921.
Heretofore, however, the aforesaid method has not been put to practical use because it cannot fulfill the requirements of the magnetron anode. The electric properties of all resonance cavities including the resonance cavity corresponding to the airtight seam of the cylinder should be substantially the same. Therefore cylinders of satisfactory roundness and uniform circumferential wall thickness should be manufactured with high industrial reliability, and the seam between both end faces of the plate piece or material should entirely be closed over the whole length thereof with high accuracy to provide well-balanced airtightness thereat.